Lunchtime Demo Fusor

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Michael Bretti
Posts: 175
Joined: Tue Aug 01, 2017 12:58 pm
Real name: Michael Bretti

Lunchtime Demo Fusor

Post by Michael Bretti »

Late last year, maybe in October or so, I got around to building a very quick and dirty demo fusor with some junk and spare parts lying around the lab I work at over a couple of lunch breaks. I originally found a small stainless vacuum chamber that was thrown away in the university tech docks trash maybe a year before, and finally got around to putting it to use since I didn't have a vacuum pump for myself at the time. I added a simple acrylic viewport on the bottom that was bolted between the bottom flange and a metal adapter using a rubber gasket I punched out of some spare rubber sheet, which worked perfectly fine for the low vacuum I was achieving. The demo fusor uses two simple spiral grids made from copper wire, filled with just plain residual air for the plasma gas. It is powered with a variac controlled, current-limited, full-wave rectified MOT for simplicity. I pumped the chamber down with a Welch Duo Seal 1400 pump. There was no instrumentation or vacuum gauges to check the pressure, so I do not know what vacuum it reached, but it was sufficient for a nicely stable and confined plasmoid with very little effort. The first wire I used for the inner grid rapidly overheated due to it being made of copper and having been far too thin, nearly melting after about 10 seconds of running. I swapped it out with a very thick heavier gauge wire which still glowed red hot during operation but lasted much longer. I managed to get a couple of good pictures of the plasmoid during operation.

Here you can see the first grid assembly with the thin wire before it overheated, operating in jet mode:
20151005_104430.jpg
Here is the second thicker grid during pump-down before a good vacuum was attained for a plasmoid to confine:
20151005_151457.jpg
Here is the second thicker grid with the fully confined plasmoid, also operating in jet mode:
20151005_150147.jpg
This demo fusor was just for fun and to see if I could do it with the scraps lying around. While it was not intended for anything more than a fun side project, I do plan on eventually designing and building a fully fusion capable fusor for the new student nuclear classroom at the lab as a learning and teaching tool (obviously not with this setup.)
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Richard Hull
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Real name: Richard Hull

Re: Lunchtime Demo Fusor

Post by Richard Hull »

Nice system on the cheap. Looks like you are between 100-50 microns on the bugle jet. I have added you to the Plasma club.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Michael Bretti
Posts: 175
Joined: Tue Aug 01, 2017 12:58 pm
Real name: Michael Bretti

Re: Lunchtime Demo Fusor

Post by Michael Bretti »

Thanks for the add! I forgot that there was a plasma club in addition to a neutron club. Even though it is pretty trivial compared to a fully neutron producing system, it is really encouraging to push forward with more advanced experiments, and hopefully I will have the chance to join the neutron club one day. You really have a lot of experience and insight to gauge the level of vacuum from just the pictures alone too - it's definitely very helpful to have an idea of the range it was operating at.
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Richard Hull
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Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: Lunchtime Demo Fusor

Post by Richard Hull »

As noted in the fusioneer's preamble, the plasma club is an expression that such a person within it has got up off their behind and actually done something to a limited degree towards the fusion effort!!

We find about 95%, or more, of those who make the plasma club, never do fusion for a whole host of reasons.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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